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Volume 26 Issue 1
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GENERAL
Full Poncelet Theorem in Minkowski dS and AdS Spaces
WANG Yao-Xiong, FAN Heng, SHI Kang-Jie, WANG Chun, ZHANG Kai, ZENG Yu
Chin. Phys. Lett. 2009, 26 (1): 010201 .   DOI: 10.1088/0256-307X/26/1/010201
Abstract   PDF(pc) (270KB) ( 670 )

We study the reflection of a straight line or a billiard on a plane in an n-dimensional Minkowski space. It is found that the reflection law coincides with that defined with respect to confocal quadratic surfaces in projective geometry. We then establish the full Poncelet theorem which holds in projective geometry in n-dimensional Minkowski space and in their quadratic surfaces including de Sitter and AdS spaces.

Inverse Scattering Method and Soliton Solution Family for String Effective Action
GAO Ya-Jun
Chin. Phys. Lett. 2009, 26 (1): 010202 .   DOI: 10.1088/0256-307X/26/1/010202
Abstract   PDF(pc) (181KB) ( 952 )

A modified Hauser--Ernst-type linear system is established and used to develop an inverse scattering method for solving the motion equations of the string effective action describing the coupled gravity, dilaton and Kalb-Ramond fields. The reduction procedures in this inverse scattering method are found to be fairly simple, which makes the proposed inverse scattering method applied fine and effective. As an application, a concrete family of soliton solutions for the considered theory is obtained.

Generalized Mei Conserved Quantity of Mei Symmetry for Mechanico-electrical Systems with Nonholonomic Controllable Constraints
XIA Li-Li, ZHAO Xian-Lin
Chin. Phys. Lett. 2009, 26 (1): 010203 .   DOI: 10.1088/0256-307X/26/1/010203
Abstract   PDF(pc) (206KB) ( 640 )
On the basis of the total time derivative along the trajectory, we study the generalized Mei conserved quantity of Mei symmetry for mechanico-electrical systems with nonholonomic controllable constraints. Firstly, the definition and criterion of Mei symmetry for mechanico-electrical systems with nonholonomic controllable constraints are presented. Secondly, a coordination function is introduced, and the conditions of existence of generalized Mei conserved quantity as well as the forms are proposed. Lastly, an example is given to illustrate the application of the results.
Approximate Solution of Homotopic Mapping to Solitary Wave for Generalized Nonlinear KdV System
MO Jia-Qi
Chin. Phys. Lett. 2009, 26 (1): 010204 .   DOI: 10.1088/0256-307X/26/1/010204
Abstract   PDF(pc) (177KB) ( 592 )
We study a generalized nonlinear KdV system is studied by using the homotopic mapping method. Firstly, a homotopic mapping transform is constructed; secondly, the suitable initial approximation is selected; then the homotopic mapping is used. The accuracy of the approximate solution for the solitary wave is obtained. From the obtained approximate solution, the homotopic mapping method exhibits a good accuracy.
Entanglement Dynamics of a Three-Level Atom in Ξ Configuration
XU Hang-Shi, XU Jing-Bo
Chin. Phys. Lett. 2009, 26 (1): 010301 .   DOI: 10.1088/0256-307X/26/1/010301
Abstract   PDF(pc) (500KB) ( 602 )
Dynamical behaviour of entanglement between the cavity mode and a three-level atom in the Ξ configuration is studied by making use of log-negativity. The influence of initial temperature of the thermal field and detuning on the entanglement is investigated. It is found that the maximal values of entanglement decreases with the temperature of the thermal field and can be controlled by the detuning.
Threshold Quantum Secret Sharing of Secure Direct Communication
LI Bao-Kui, YANG Yu-Guang, , WEN Qiao-Yan
Chin. Phys. Lett. 2009, 26 (1): 010302 .   DOI: 10.1088/0256-307X/26/1/010302
Abstract   PDF(pc) (228KB) ( 644 )
We propose a (t,n)-threshold quantum secret sharing protocol of secure direct communication following some ideas of Zhang's protocol [Phys. Lett. A 342 (2005) 60] and Tokunaga et al.'s protocol [Phys. Rev. A 71 (2005) 012314]. The sender distributes the classical secret shares to his or her n agents and each agent owns a secret share in advance. The sender's secure direct communication message can be extracted by an agent subset by collaboration in such a way that at least t or more agents can obtain the secret message with the mutual assistances but any t-1 or fewer agents cannot. In contrast to the previous multiparty quantum secret sharing protocols in which the sender's secret message can be recovered only if all the agents collaborate, our protocol is more practical and more flexible
Novel Quantum Secret Sharing and Controlled Communication Schemes Based on Einstein-Podolsky-Rosen Correlations
LI Yuan, ZENG Gui-Hua
Chin. Phys. Lett. 2009, 26 (1): 010303 .   DOI: 10.1088/0256-307X/26/1/010303
Abstract   PDF(pc) (205KB) ( 525 )
Employing quantum registers, we first proposed a novel (2, 3) quantum threshold scheme based on Einstein-Podolsky-Rosen (EPR) correlations in this letter. Motivated by the present threshold scheme, we also propose a
controlled communication scheme to transmit the secret message with a controller. In the communication protocol, the encoded quantum message carried by particles sequence, is transmitted by legitimate communicators.
Fermion Tunnelling of a New Form Finslerian Black Hole
LIN Kai, YANG Shu-Zheng
Chin. Phys. Lett. 2009, 26 (1): 010401 .   DOI: 10.1088/0256-307X/26/1/010401
Abstract   PDF(pc) (184KB) ( 443 )

We improve the fermion tunnelling theory proposed by Kerner and Mann, and research into the fermion tunnelling radiation from a Finslerian black hole. The Finsler black hole put forward by Rutz is a solution of Einstein's vacuum field equations in Finsler theory. We study the radiation from the black hole with a semi-classical method, and the result proves that the tunnelling rate depends on the tangent vector.

Oscillations and Collapses of Proto--Neutron Stars
LU Jun-Li, Wan Mew-Bing
Chin. Phys. Lett. 2009, 26 (1): 010402 .   DOI: 10.1088/0256-307X/26/1/010402
Abstract   PDF(pc) (237KB) ( 363 )

We examine the oscillation and collapse of a relativistic star, e.g., a proto--neutron star, with an equation of state (EOS) which is slowly changing as driven by, e.g., losing of thermal energy through radiations. We find that the frequency of the fundamental mode of oscillation (radial) will gradually increase then abruptly drop to zero when the star gets close to the point of instability. We also find that for a wide range of configurations on the unstable branch of equilibrium configurations, the collapse is dominated by one unstable mode.

Measurement of Density Inhomogeneity for Source Masses in Time-of-Swing Method of Measuring
LIU Lin-Xia, SHAO Cheng-Gang, TU Liang-Cheng, LUO Jun
Chin. Phys. Lett. 2009, 26 (1): 010403 .   DOI: 10.1088/0256-307X/26/1/010403
Abstract   PDF(pc) (384KB) ( 564 )

A method with scanning electron microscopy (SEM) is presented to measure the density inhomogeneity of the stainless steel (SS316) sphere prepared for measuring G using time-of-swing method. The experimental result shows that the relative density inhomogeneity of the sphere is better than 5.9×10-4 over the volume of 0.272×0.234×0.005mm3. If we assume that the density inhomogeneity of the spheres used in our G measurement is the same as that of the sphere destroyed in testing, it will contribute to G value with an uncertainty of less than 0.034ppm in our G measurement. Furthermore, the mass centre offset from the geometric centre of the sphere will be less than 4.3×10-4,μm due to this inhomogeneity.

String Cosmological Models in Five-Dimensional Spacetimes
Sanjay Oli
Chin. Phys. Lett. 2009, 26 (1): 010404 .   DOI: 10.1088/0256-307X/26/1/010404
Abstract   PDF(pc) (143KB) ( 630 )
We present some classes of solutions for dust matter coupled to the string cloud in five-dimensional Kaluza-Klein spacetimes. The solutions have one or two distinct singularities depending upon the sign of the constant of integration. Some of the classes of models exhibit inflation in the initial stage. The behaviour of associated parameters has been discussed in detail.
Generalized Projective Synchronization between Two Complex Networks with Time-Varying Coupling Delay
SUN Mei, ZENG Chang-Yan, TIAN Li-Xin
Chin. Phys. Lett. 2009, 26 (1): 010501 .   DOI: 10.1088/0256-307X/26/1/010501
Abstract   PDF(pc) (249KB) ( 652 )

Generalized projective synchronization (GPS) between two complex networks with time-varying coupling delay is investigated. Based on the Lyapunov stability theory, a nonlinear controller and adaptive updated laws are designed. Feasibility of the proposed scheme is proven in theory. Moreover, two numerical examples are presented, using the energy resource system and Lü's system [Physica A 382(2007)672] as the nodes of the networks. GPS between two energy resource complex networks with time-varying coupling delay is achieved. This study can widen the application range of the generalized synchronization methods and will be instructive for the demand--supply of energy resource in some regions of China.

Criticality of Epidemic Spreading in Mobile Individuals Mediated by Environment
HE Min-Hua, ZHANG Duan-Ming, FANG Pin-Jie, LI Zhi-Cong, WANG Hai-Yan
Chin. Phys. Lett. 2009, 26 (1): 010502 .   DOI: 10.1088/0256-307X/26/1/010502
Abstract   PDF(pc) (357KB) ( 380 )
We investigate the critical behaviour of an epidemical model in a diffusive population mediated by a static vector environment on a 2D network. It is found that this model presents a dynamical phase transition from disease-free state to endemic state with a finite population density. Finite-size and
short-time dynamic scaling relations are used to determine the critical population density and the critical exponents characterizing the behaviour near the critical point. The results are compatible with the universality class of directed percolation coupled to a conserved diffusive field with equal diffusion
constants.
Evolutions of Wave Patterns in Whitham-Broer-Kaup Equation
ZHANG Zheng-Di, BI Qin-Sheng
Chin. Phys. Lett. 2009, 26 (1): 010503 .   DOI: 10.1088/0256-307X/26/1/010503
Abstract   PDF(pc) (278KB) ( 447 )

Upon investigation of the parameter influence on the structure of WBK equation, transition boundaries are derived. All possible bounded waves as well as the existence conditions are obtained. The evolution of waves with variation of the parameters is discussed in detail, which reveals the bifurcation mechanism between different wave patterns.

Raman Scattering Spectroscopy of Phase Transition in n-Pentadecane under High Temperature and High Pressure
QIAO Er-Wei, ZHENG Hai-Fei, XU Bei
Chin. Phys. Lett. 2009, 26 (1): 010701 .   DOI: 10.1088/0256-307X/26/1/010701
Abstract   PDF(pc) (320KB) ( 456 )

The Raman spectroscopy of n-pentadecane is investigated in a moissanite anvil cell at normal temperatures and a diamond anvil cell under pressure to about 3000MPa and at temperature from 298 to 573K. Result indicates that at room temperature the vibration modes, assigned to the symmetric and asymmetric stretching of CH3 and CH2 stretching, shift to higher frequency and display a pressure dependent quasi-linear curve. A liquid--solid phase transition appears at a pressure of 150MPa. The high temperature solidus line of n-pentadecane follows a quadratic function of P=0.02369T2-9.117T+725.58, in agreement with previous conclusion derived from studies of other hydrocarbons. Upon phase transition, fitting the experimental data obtained in a temperature range of 283-553K to the Clausius--Clapeyron equation allows one to define the thermodynamic parameters of n-pentadecane of dP/dT=0.04738T -9.117.

THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Electric-Wiggler-Enhanced Three-Quantum Scattering and the Output Power Affected by this Scattering in a Free-Electron Laser
S. H. Kim
Chin. Phys. Lett. 2009, 26 (1): 011201 .   DOI: 10.1088/0256-307X/26/1/011201
Abstract   PDF(pc) (202KB) ( 482 )

We derive the cross section of scattering through the three-quantum interaction of an electron with the incident laser field, the emitted photon, and an axial electrostatic field produced by the magnetic wiggler in the magnetic wiggler acting as the sole zeroth-order perturbing classical field in the first free-electron laser (FEL). In the derivation, we apply quantum-wiggler electrodynamics (QWD). We find that this scattering predominates the usual two-quantum scattering. The output power of spontaneous free-electron two-quantum Stark emission driven by the above electrostatic field attenuated by the three-quantum scattering agrees within a factor of 10 with the measured power in the case of the first FEL.

Effect of Hidden Colour Channel on H Particle in Chiral Quark Model
BI Zheng, PANG Hou-Rong, PING Jia-Lun
Chin. Phys. Lett. 2009, 26 (1): 011202 .   DOI: 10.1088/0256-307X/26/1/011202
Abstract   PDF(pc) (237KB) ( 393 )
The structure of the H particle is studied in the framework of chiral quark model by solving the resonating group equation of coupled-channel. Four physical channels and eleven hidden colour channels are taken into account. Hidden colour channel coupling is found to cause an obvious decrease of eigenenergy of the H particle (about 10MeV). The most favourable hidden colour channel of the H particle is given.
Calculation of Nuclear Deeply Virtual Compton Scattering in HERMES Experiment
YE Hong-Xue, MAO Ya-Jun, WANG Si-Guang, SUN Bo
Chin. Phys. Lett. 2009, 26 (1): 011301 .   DOI: 10.1088/0256-307X/26/1/011301
Abstract   PDF(pc) (302KB) ( 348 )

We investigate the possibility to acquire information of nuclear generalized parton distribution (GPD) H by studying the deeply virtual Compton scattering (DVCS) off several nuclear targets at the HERMES group (Hadron-Electron Ring Accelerator Measurement of Spin). Two different models are used and developed to demonstrate the leading asymmetry amplitude ALUsinΦ for coherent-enriched and incoherent-enriched parts with both statistical and systematic uncertainties estimated. It is found that a clear enhancement of ratio of nuclear asymmetry ALUA,sinΦ to free proton asymmetry ALUH,sinΦ in the coherent-enriched region is expected by both models, and a decrease of the ratio in incoherent-enriched region; both give the information about nuclear modifications. It is also possible to distinguish between those two models even under the limited statistics.

Experimental Sensitivities on Searching for Rare and Forbidden Decays of Charm Mesons at BES-III
ZHAO Ming-Gang, RONG Gang, MA Hai-Long
Chin. Phys. Lett. 2009, 26 (1): 011401 .   DOI: 10.1088/0256-307X/26/1/011401
Abstract   PDF(pc) (241KB) ( 373 )
We discuss the Monte Carlo studies of searching for the rare and forbidden pure-leptonic and semi-leptonic decays of D+,0 and D+s mesons, based on a full Monte Carlo simulation for the BES-III detector, with the BES-III Offline Software System. The experimental sensitivities of searching for 36 rare and forbidden charm meson decays are estimated.
NUCLEAR PHYSICS
Self-affine Multiplicity Fluctuation of Slow Particles in 16O-AgBr Collisions at 3.7 A GeV
LI Jun-Sheng, ZHANG Dong-Hai, LI Hui-Ling, LIU Fu-Hu
Chin. Phys. Lett. 2009, 26 (1): 012401 .   DOI: 10.1088/0256-307X/26/1/012401
Abstract   PDF(pc) (288KB) ( 420 )
We study the slow particles in 16O-AgBr collisions at 3.7 A GeV in nuclear emulsion with the method of two-dimensional factorial moments using the Hurst exponent. Our investigation reveals the power law behaviour,
exhibited in self-affine analysis, better than that in self-similar analysis. This work shows a clear evidence of self-affine target fragmentation.
ATOMIC AND MOLECULAR PHYSICS
Molecular Dynamics Simulation of Bubble Nucleation in Explosive Boiling
ZOU Yu, HUAI Xiu-Lan, LIANG Shi-Qiang
Chin. Phys. Lett. 2009, 26 (1): 013101 .   DOI: 10.1088/0256-307X/26/1/013101
Abstract   PDF(pc) (526KB) ( 600 )

Molecular dynamics (MD) simulation is carried out for the bubble nucleation of liquid nitrogen in explosive boiling. The heat is transferred into the simulation system by rescaling the velocity of the molecules. The results indicate that the initial equilibrium temperature of liquid and molecular cluster size affect the energy conversion in the process of bubble nucleation. The potential energy of the system violently varies at the beginning of the bubble nucleation, and then varies around a fixed value. At the end of bubble nucleation, the potential energy of the system slowly increases. In the bubble nucleation of explosive boiling, the lower the initial equilibrium temperature, the larger the size of the molecular cluster, and the more the heat transferred into the system of the simulation cell, causing the increase potential energy in a larger range.

Finite Space Complete Basis Method: Precision Computation of High-Resolution Spectrum near Ionization Threshold
GAO Xiang, CHEN Shao-Hao, LI Jia-Ming,
Chin. Phys. Lett. 2009, 26 (1): 013102 .   DOI: 10.1088/0256-307X/26/1/013102
Abstract   PDF(pc) (246KB) ( 399 )

A new method is proposed to describe quantum dynamical processes in finite space by using of a set of discretized complete bases. In this method, the finite space complete basis is obtained by solving the self-consistent field equation with reflecting boundary conditions. Hence, both negative and positive orbital energies can be obtained. Such method can be used in systems which involve dynamics only in the reaction zone, i.e., in a finite space. To illustrate the validity of the method, we present two examples: theoretical calculation of the high excited states spectra including the continuum of sodium and barium.

Fragmentation of CO in Femtosecond Laser Fields
GUO Wei, ZHU Jing-Yi, WANG Bing-Xing, WANG Yan-Qiu, WANG Li
Chin. Phys. Lett. 2009, 26 (1): 013201 .   DOI: 10.1088/0256-307X/26/1/013201
Abstract   PDF(pc) (456KB) ( 465 )
Fragmentation of CO in a linearly polarized femtosecond laser field within the intensity order of 1014W・cm-2 at 820nm is investigated experimentally by using velocity mapping technique. According to the observed kinetic energy and angular distributions of different charged fragment ions, fragmentation channels of CO are proposed. The angular distributions provide helpful information for assigning the dissociation channels.
Rosen--Zener Transition in a Nonlinear System for Two-Component Bose--Einstein Condensates in Optical Lattices
JIANG Xin, LIN Mai-Mai, LI Sheng-Chang, DUAN Wen-Shan
Chin. Phys. Lett. 2009, 26 (1): 013701 .   DOI: 10.1088/0256-307X/26/1/013701
Abstract   PDF(pc) (642KB) ( 613 )
We study the Rosen-Zener transition (RZT) in a nonlinear system for two-component Bose--Einstein condensates in optical lattices. It is found that the percentage of the components could affect the quantum transition dramatically. For the component with large percentage it is equivalent that the effect of the nonlinearity is stronger, whereas for the component with small percentage the effect is weaker. We also find that the nonlinearity c11 can affect the quantum transition dramatically. This is similar to that reported from Ref.[14]. Compared with one-component systems, however, the effect of the nonlinearity is decreased due to the two components of the BECs in optical lattices. Furthermore, the effect of the coupling nonlinearity between two components c12 is studied. The component with large percentage is more affected by the nonlinearity than that with small-percentage component
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
Positive and Negative Lateral Shifts from an Anisotropic Metamaterial Slab Backed by a Metal
CHENG Min, CHEN Rong
Chin. Phys. Lett. 2009, 26 (1): 014101 .   DOI: 10.1088/0256-307X/26/1/014101
Abstract   PDF(pc) (225KB) ( 513 )

The lateral shift of a light beam at the surface of an anisotropic metamaterial (AMM) slab backed by a metal is investigated. Analytical expressions of the lateral shifts are derived using the stationary-phase method, in the case that total reflection does and does not occur at the first interface. The sign of the lateral shift in two situations is discussed, and the necessary conditions for the lateral shift to be positive or negative are given. It is shown that the thickness and physical parameters of the AMM slab and the incident angle of the light beam strongly affect the properties of the lateral shift. Numerical results validate these conclusions. The lossy effect of the metamaterial on the lateral shift is also investigated.

Simulation of Electromagnetic Wave Logging Response in Deviated Wells Based on Vector Finite Element Method
LV Wei-Guo, CHU Zhao-Tan, ZHAO Xiao-Qing, FAN Yu-Xiu, SONG Ruo-Long, HAN Wei
Chin. Phys. Lett. 2009, 26 (1): 014102 .   DOI: 10.1088/0256-307X/26/1/014102
Abstract   PDF(pc) (384KB) ( 806 )
The vector finite element method of tetrahedral elements is used to model 3D electromagnetic wave logging response. The tangential component of the vector field at the mesh edges is used as a degree of freedom to overcome the shortcomings of node-based finite element methods. The algorithm can simulate inhomogeneous media with arbitrary distribution of conductivity and magnetic permeability. The electromagnetic response of well logging tools are studied in dipping bed layers with the borehole and invasion included. In order to simulate realistic logging tools, we take the transmitter antennas consisting of circular wire loops instead of magnetic dipoles. We also investigate the apparent resistivity of inhomogeneous formation for different dip angles
A Laser-Diode End-Pumped Nd:YVO4 Slab Laser at 1342nm
YAN Ying, ZHANG Heng-Li, LIU Yang, XING Ji-Chuan, XIN Jian-Guo
Chin. Phys. Lett. 2009, 26 (1): 014201 .   DOI: 10.1088/0256-307X/26/1/014201
Abstract   PDF(pc) (266KB) ( 486 )
A laser-diode end-pumped Nd:YVO4 slab laser with a flat-concave stable cavity at 1342nm is demonstrated. Under the pumping power of 92W, a cw laser of output 17.8W is obtained with the slope efficiency of 25.6%.
Generation of Optical Vortex Using a Spiral Phase Plate Fabricated in Quartz by Direct Laser Writing and Inductively Coupled Plasma Etching
CHEN Jun, KUANG Deng-Feng, GUI Min, FANG Zhi-Liang
Chin. Phys. Lett. 2009, 26 (1): 014202 .   DOI: 10.1088/0256-307X/26/1/014202
Abstract   PDF(pc) (362KB) ( 1439 )
A simple, economical and reliable technique is proposed for fabricating a spiral phase plate (SPP) in a quartz substrate to generate optical vortex with a unit topological charge at the wavelengths of 632.8nm. The spiral phase plate is first formed in the photoresist by direct laser writing lithography and then transferred into the quartz substrate by inductively coupled plasma etching. The performance of the fabricated SPP is verified by using beam intensity distribution, which is in agreement with the theoretical calculation result. The interference measurement suggests that we have succeeded to generate optical vortex with a unit topological charge with the fabricated SPP.
Characteristics of Cladding-Pumped Short Er3+/Yb3+ Codoped Single Mode Phosphate Glass Fibre
XU Shan-Hui, YANG Zhong-Min, XU Wen-Cheng, QIU Dong-Lai, ZHANG Qin-Yuan, JIANG Zhong-Hong
Chin. Phys. Lett. 2009, 26 (1): 014203 .   DOI: 10.1088/0256-307X/26/1/014203
Abstract   PDF(pc) (301KB) ( 653 )
We experimentally investigate the laser characteristics of a series of short pieces of newly-developed Er3+/Yb3+ codoped single mode phosphate glass fibres via the cladding pump of a 976nm multimode laser diode. A stable
continuous-wave single transverse mode laser with over 85mW at 1553nm is generated from a 5.5-cm-long active fibre. Single mode laser output power per unit length is up to 15mW/cm. Moreover, the slope efficiency is 11.8% when the pump power is below 940mW and the 3dB linewidth is 0.06nm at the maximum pump power. The numerical simulation results show that the laser emission slope efficiency can exceed 20% by means of increasing the coupling efficiency of the pump to the fibre core further.
A Sensor-on-Chip Based on Second-Order Optical Effect of ZnO Nanowires
ZHU Jing, ZHU Guang-Ping, LU Chang-Gui, XU Chun-Xiang, CUI Yi-Ping
Chin. Phys. Lett. 2009, 26 (1): 014204 .   DOI: 10.1088/0256-307X/26/1/014204
Abstract   PDF(pc) (364KB) ( 424 )

Strong second-order nonlinear effect of ZnO nanowires on a silicon wafer are demonstrated by using the hyper-Rayleigh scattering (HRS) measurement. The large nonlinear effect can be attributed to the following two factors: (1) the large total dipole moment caused by high surface defect density and electrostatic potential gradient, (2) coherent effect due to high crystal quality of single nanowire. Moreover, the second-order nonlinear effect is found to become weaker when the chip is put into organic solvent due to modification of surface defect caused by organic molecules. The variation of second-order signal in the solvent indicated the potential applications of ZnO nanowires as a sensor-on-chip (SoC).

Analysis of Nanostructural Waveguides Using Fourth-Order Accurate Finite Difference Methods with Nonuniform Scheme
JI Yang, YUN Bin-Feng, HU Guo-Hua, CUI Yi-Ping
Chin. Phys. Lett. 2009, 26 (1): 014205 .   DOI: 10.1088/0256-307X/26/1/014205
Abstract   PDF(pc) (236KB) ( 426 )

We successfully apply fourth-order accurate finite difference methods with nonuniform scheme to analysis the symmetric slot waveguides. The results of numerical simulations show that the present nonuniform formula offers the results more accurate than the previously presented second order schemes.

Characteristics of a Cataphoresis He-Ca+ Recombination Laser
CHEN Li, PAN Bai-Liang, WANG Ya-Juan, MAO Bang-Ning
Chin. Phys. Lett. 2009, 26 (1): 014206 .   DOI: 10.1088/0256-307X/26/1/014206
Abstract   PDF(pc) (306KB) ( 392 )
A cataphoretic input of calcium vapour into the active volume of pulsed He-Ca+ laser is designed and made. The recombination laser at 373.3nm and the R-M transition laser at 854.6nm are achieved experimentally with modified Blumlein circuit by high-frequency longitudinal pulsed discharge. The dependences of work parameters such as the pulse frequency, the power supply voltage and the helium pressure on laser output characteristics at 373.3nm line are measured and discussed. The maximum laser output power of 136mW and the specific power of 5.9mW/cm3 are obtained, respectively
Coloured Conical Emission in BBO Crystal Pumped by Second Harmonic Femtosecond Pulses
BI Jie, LI Yu-Hua, YIN Juan-Juan, LU Pei-Xiang
Chin. Phys. Lett. 2009, 26 (1): 014207 .   DOI: 10.1088/0256-307X/26/1/014207
Abstract   PDF(pc) (436KB) ( 416 )

Coloured conical emission (CCE) is investigated experimentally in a β-barium borate crystal excited by intense second harmonic femtosecond pulses. Contrary sequences of green and red conical emission with variable diameters are observed at different incidence angles, which is consistent with the calculation results based on the phase matching condition. As its broad range spectrum, CCE offers an alternative means to produce an ultrafast broadband light source. It is found that the spectrum of green CE shifts toward longer wavelengths as the length of BBO crystal increased. .

Energy Squeeze of Ultrashort Light Pulse by Kerr Nonlinear Photonic Crystals
LIU Ye, ZHOU Fei, ZHANG Dao-Zhong, LI Zhi-Yuan
Chin. Phys. Lett. 2009, 26 (1): 014208 .   DOI: 10.1088/0256-307X/26/1/014208
Abstract   PDF(pc) (325KB) ( 588 )
Self-phase modulation can efficiently shape the spectrum of an optical pulse propagating along an optical material with Kerr nonlinearity. In this work we show that a one-dimensional Kerr nonlinear photonic crystal can impose anomalous spectrum modulation to a high-power ultrashort light pulse. The spectrum component at the photonic band gap edge can be one order of magnitude enhanced in addition to the ordinary spectrum broadening due to self-phase modulation. The enhancement is strictly pinned at the band gap edge by changing the sample length, the intensity or central wavelength of the incident pulse. The phenomenon is attributed to band gap induced enhancement of light-matter interaction.
Light Localization in Slot Photonic Crystal Waveguide
WU Jun, PENG Chao, LI Yan-Ping, WANG Zi-Yu
Chin. Phys. Lett. 2009, 26 (1): 014209 .   DOI: 10.1088/0256-307X/26/1/014209
Abstract   PDF(pc) (396KB) ( 641 )
A single-mode photonic crystal waveguide with a linear tapered slot is presented, which can localize light spatially by changing the slot width. Its effective bandwidth is 52nm, from 1500nm to 1552nm. Along the tapered structure, the slot width is reduced, and the corresponding band curve shifts. The group velocity of light becomes zero at the band edge. Therefore, different frequency components of the guided light are slowed down and finally localized at correspondingly different widths inside a tapered slot photonic crystal waveguide. Furthermore, this structure can confine light wave in a narrow slot waveguide, which may effectively enhance the interaction between light and the low-index wave-guiding materials filled in the slot.
Teleporting an Unknown Two-qubit Entangled State via Ion-Trap Systems
AI Ling-Yan, DU Gang, ZHU Shi-Liang, ZHANG Zhi-Ming
Chin. Phys. Lett. 2009, 26 (1): 014210 .   DOI: 10.1088/0256-307X/26/1/014210
Abstract   PDF(pc) (225KB) ( 685 )

We propose a scheme for teleportation of an unknown two-qubit entangled state via trapped ions. In this scheme, we use the GHZ state as a quantum channel and the success probability can reach 1. The distinct advantage of our scheme is insensitive to the heating of the vibrational mode. In addition, Bell-state measurement is not required.

Near-Field Optical Transfer Function for Far-Field Super-Resolution Imaging
ZHANG Zhi-You, DU Jing-Lei, GUO Yong-Kang, NIU Xiao-Yun, LI Min, LUOXian-Gang, DU Chun-Lei
Chin. Phys. Lett. 2009, 26 (1): 014211 .   DOI: 10.1088/0256-307X/26/1/014211
Abstract   PDF(pc) (419KB) ( 594 )
The far-field superlens based on surface plasmon polaritons (SPP) has shown great application potential, but it is difficult and time-consuming to reconstruct the far-field image. We derive a near-field optical transfer function (NOTF) of a silver slab and analyse its validity so that accurate information of nano-scale object in the near-field can be computed rapidly. The NOTF is helpful not only for analysing the super-resolution imaging process in far-field, but also for providing a track to describe the transmission of optical information from near-field to far-field by using the optical transfer functions theory only.
Observation of Antiphase State in a Self-Q-switched Nd,Cr:YAG Laser
SHI Yu-Xian, LI Qi-Nan, DU Shi-Feng, ZHANG Dong-Xiang, ZHANG Zhi-Guo, FENG Bao-Hua, ZHANG Shi-Wen
Chin. Phys. Lett. 2009, 26 (1): 014212 .   DOI: 10.1088/0256-307X/26/1/014212
Abstract   PDF(pc) (488KB) ( 477 )
We experimentally investigate the antiphase dynamics phenomenon in a self-Q-switched Nd,Cr:YAG laser operating at 946 nm. Due to the effect of spatial hole burning, the Q-switched pulses sequences of one, two and three modes at different pump power are observed. The experimental results show that the pulse sequences display classic antiphase dynamics.
Nd:YAG Lasers Operating at 1064nm and 946nm by Direct Pumping and Thermally Boosted Pumping
XU Chang-Wen, WEI Zhi-Yi, HE Kun-Na, LI De-Hua, ZHANG Yong-Dong, ZHANGZhi-Guo
Chin. Phys. Lett. 2009, 26 (1): 014213 .   DOI: 10.1088/0256-307X/26/1/014213
Abstract   PDF(pc) (348KB) ( 752 )

We demonstrate a 1064nm Nd:YAG laser by directly pumping into the upper lasing level with a tunable Ti:sapphire laser. The valid wavelength is demonstrated at 868.3nm, 875.2nm, 883.8nm, and 885.5nm, respectively. To our knowledge, this is the first time that 1064nm Nd:YAG laser pumped by 875.2nm laser. In addition, laser wavelength at 946nm is also generated by direct pumping together with traditional pumping.

Metamorphic InGaAs Quantum Well Laser Diodes at 1.5μm on GaAs Grown by Molecular Beam Epitaxy
WANG Hai-Li, WU Dong-Hai, WU Bing-peng, NI Hqiao-Qiao, HUANG She-Song, XIONG Yong-Hua, WANG Peng-Fei, HAN Qin, NIU Zhi-Chuan, I.Tå, ngring, S. M. Wang
Chin. Phys. Lett. 2009, 26 (1): 014214 .   DOI: 10.1088/0256-307X/26/1/014214
Abstract   PDF(pc) (404KB) ( 784 )
We report a 1.5-μm InGaAs/GaAs quantum well laser diode grown by molecular beam epitaxy on InGaAs metamorphic buffers. At 150K, for a 1500×10μm2 ridge waveguide laser, the lasing wavelength is centred at 1.508μm and the threshold current density is 667A/cm2 under pulsed operation. The pulsed lasers can operate up to 286K.
Influence of Non-uniform Temperature Field on Spectra of Fibre Bragg Grating
ZHOU Yan, HE Xing-Fang, YUAN Jie, YIN Li-Qun, FANG Xiao-Yong, CAO Mao-Sheng
Chin. Phys. Lett. 2009, 26 (1): 014215 .   DOI: 10.1088/0256-307X/26/1/014215
Abstract   PDF(pc) (388KB) ( 696 )
We simulate the spectrum characteristics of fibre Bragg grating (FBG) with non-uniform temperature using the transmission matrix method, and the results are analysed. It is found that firstly the modulated coefficient of average refractive index is a very important parameter that influences the spectrum characteristic of the fibre Bragg grating, and secondly the spectrum curves are different in different temperature fields at the same parameter. Hence, we can determine the metrical temperature by analysing the spectrum of fibre Bragg grating.
Condition of Retrieving Vertical Column Density of Atmospheric Pollution Gases by Using Scattered Solar Radiation
ZUO Hao-Yi, LUO Shi-Rong
Chin. Phys. Lett. 2009, 26 (1): 014216 .   DOI: 10.1088/0256-307X/26/1/014216
Abstract   PDF(pc) (392KB) ( 379 )

We present a method to monitor the vertical column density (VCD) of atmospheric pollution gases by using the scattered solar radiation. The necessary condition of capturing the useful scattered solar radiation is achieved. The condition is only dependent on the solar elevation angle, while independent of the solar azimuth angle, which could greatly simply the capturing equipment and procedure. Under the condition, the VCD of tropospheric NO2 in Chengdu, China is retrieved from the scattered solar radiation, which is close to that from the direct solar radiation.

Extraordinary Resonant Scattering in Imperfect Acoustic Cloak
CHENG Ying, LIU Xiao-Jun
Chin. Phys. Lett. 2009, 26 (1): 014301 .   DOI: 10.1088/0256-307X/26/1/014301
Abstract   PDF(pc) (465KB) ( 630 )
We present a systematic study on the extraordinary resonant scattering in imperfect acoustic cloak by means of acoustic scattering theory. Analysis results demonstrate that the resonances are inevitable due to the perturbation to the ideal cloak, and specific resonance modes are excited by specific order waves. The strength of resonance is determined by the magnitude of perturbation and each order wave's sensitivity to the perturbation. Further studies reveal the unique scattering characters of different resonance modes.
A Unique Method to Describe the Bonding Strength in a Bonded Solid-S-olid Interface by Contact Acoustic Nonlinearity
CHEN Jian-Jun, ZHANG De, MAO Yi-Wei, CHENG Jian-Chun
Chin. Phys. Lett. 2009, 26 (1): 014302 .   DOI: 10.1088/0256-307X/26/1/014302
Abstract   PDF(pc) (345KB) ( 445 )
We present a unique method to describe the bonding strength at a bonded solid-solid interface in a multilayered composite material by contact acoustic nonlinearity (CAN) parameter. A CAN model on the bonded solid--solid interface is depicted. It can be seen from the model that CAN parameter is very sensitive to the bonding strength at the interface. When an incident
focusing acoustic longitudinal wave scans the interface in two dimensions, the transmitted wave can be used to extract CAN parameter. The contour of the bonding strength for a sample is obtained by CAN parameter. The results show that the region with weak bonding strength can be easily distinguished from the contour.
Exact Invariants for a Time-Dependent Hamiltonian System
LUO Xiao-Bing
Chin. Phys. Lett. 2009, 26 (1): 014501 .   DOI: 10.1088/0256-307X/26/1/014501
Abstract   PDF(pc) (568KB) ( 482 )

We have a classical look for a quantum system which is exactly solvable. We construct the invariant manifolds analytically, and then apply the semiclassical quantization rules in a final step to compute the quasienergies. The invariant is obtained by performing a canonical transformation of the initially time-dependent Hamiltonian to a time-independent one. The correspondence between classical and quantum mechanics is elucidated.

Multimode Coupling Theory for Kelvin-Helmholtz Instability in Incompressible Fluid
WANG Li-Feng, YE Wen-Hua, , FAN Zheng-Feng, LI Ying-Jun
Chin. Phys. Lett. 2009, 26 (1): 014701 .   DOI: 10.1088/0256-307X/26/1/014701
Abstract   PDF(pc) (375KB) ( 390 )
A weakly nonlinear model is proposed for multimode Kelvin-Helmholtz instability. The second-order mode coupling formula for Kelvin-Helmholtz instability in two-dimensional incompressible fluid is presented by expanding the perturbation velocity potential to second order. It is found that there is an important resonance in the course of the sum frequency mode coupling but the difference frequency mode coupling does not have. This resonance makes the sum frequency mode coupling process relatively complex. The sum frequency mode coupling is strongly dependent on time especially when the density of the two fluids is adjacent and the difference frequency mode coupling is not.
MHD Flow Towards a Permeable Surface with Prescribed Wall Heat Flux
Anuar Ishak, Roslinda Nazar, Ioan Pop
Chin. Phys. Lett. 2009, 26 (1): 014702 .   DOI: 10.1088/0256-307X/26/1/014702
Abstract   PDF(pc) (189KB) ( 441 )
The steady magnetohydrodynamic (MHD) mixed convection flow towards a vertical permeable surface with prescribed heat flux is investigated. The governing partial differential equations are transformed into a system of ordinary differential equations, which is then solved numerically by a finite-difference method. The features of the flow and heat transfer characteristics for different values of the governing parameters are analysed and discussed. Both assisting and opposing flows are considered. It is found that dual solutions exist for the assisting flow, besides the solutions usually reported in the literature for the opposing flow.
Viscous Flow over an Unsteady Shrinking Sheet with Mass Transfer
FANG Tie-Gang, ZHANG Ji, YAO Shan-Shan
Chin. Phys. Lett. 2009, 26 (1): 014703 .   DOI: 10.1088/0256-307X/26/1/014703
Abstract   PDF(pc) (312KB) ( 1026 )
The unsteady viscous flow over a continuously shrinking surface with mass suction is studied. The solution is fortunately an exact solution of the unsteady Navier-Stokes equations. Similarity equations are obtained through the application of similarity transformation techniques. Numerical techniques are used to solve the similarity equations for different values of the mass suction parameters and the unsteadiness parameters. Results show that multiple solutions exist for a certain range of mass suction and unsteadiness parameters. Quite different flow behaviour is observed for an unsteady shrinking sheet from an unsteady stretching sheet.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
Mechanism of Spatiotemporal Distribution of Laser Ablated Materials
XU Rong-Qing, CUI Yi-Ping, LU Jian, NI Xiao-Wu
Chin. Phys. Lett. 2009, 26 (1): 015201 .   DOI: 10.1088/0256-307X/26/1/015201
Abstract   PDF(pc) (339KB) ( 358 )
Interaction between subsequent laser and ablated materials in laser processing changes the laser spatiotemporal distribution and has influences on the efficiency and quality of laser processing. The theoretical and experimental researches on transportation behaviour of ablated materials are provided. It is shown that the velocity distribution of ablated materials is determined by ablation mechanism. The transportation behaviour of ablated materials is controlled by diffusion mechanism and light field force during laser pulse duration while it is only determined by diffusion mechanism when the laser pulse terminates. In addition, the spatiotemporal distribution of ablated materials is presented.
Response of the Earth's Magnetosphere and Ionosphere to Solar Wind Driver and Ionosphere Load: Results of Global MHD Simulations
XIONG Ming, PENG Zhong, HU You-Qiu, ZHENG Hui-Nan
Chin. Phys. Lett. 2009, 26 (1): 015202 .   DOI: 10.1088/0256-307X/26/1/015202
Abstract   PDF(pc) (222KB) ( 477 )
Three-dimensional global magnetohydrodynamic simulations of the solar wind--magnetosphere-ionosphere system are carried out to explore the dependence of the magnetospheric reconnection voltage, the ionospheric transpolar potential, and the field aligned currents (FACs) on the solar wind driver and ionosphere load for the cases with pure southward interplanetary magnetic field (IMF). It is shown that the reconnection voltage and the transpolar potential increase monotonically with decreasing Pedersen conductance (ΣP), increasing southward IMF strength (Bs) and solar wind speed (vsw). Moreover, both regions 1 and 2 FACs increase when Bs and vsw increase, whereas the two currents behave differently in response to ∑P. As ∑P increases, the region 1 FAC increases monotonically, but region 2 FAC shows a non-monotonic response to the increase of ∑P: it first increases in the range of (0,5) Siemens and then decreases for ∑P > 5 Siemens.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
Raman Spectroscopy of Irradiation Effect in Three Carbon Allotropes Induced by Low Energy B Ions
FU Yun-Chong, JIN Yun-Fan, YAO Cun-Feng, ZHANG Chong-Hong
Chin. Phys. Lett. 2009, 26 (1): 016101 .   DOI: 10.1088/0256-307X/26/1/016101
Abstract   PDF(pc) (450KB) ( 420 )

Irradiation effect in three carbon allotropes C60, diamond and highly oriented pyrolytic graphite (HOPG) induced by 170keV B ions, mainly including the process of the damage creation, is investigated by means of Raman spectroscopy technique. The differences on irradiation sensitivity and structural stability for C60, HOPG and diamond are compared. The analysis results indicate that C60 is the most sensitive for B ions irradiation, diamond is the second one and the structure of HOPG is the most stable under B ion irradiation. The damage cross sections σ of C60, diamond and HOPG deduced from the Raman spectra are 7.78×10-15, 6.38×10-15 and 1.31×10-15cm2, respectively.

Pressure-Induced Phase Transition of Ruthenium Diboride
REN Feng-Zhu, WANG Yuan-Xu, ZHANG Guang-Biao
Chin. Phys. Lett. 2009, 26 (1): 016102 .   DOI: 10.1088/0256-307X/26/1/016102
Abstract   PDF(pc) (286KB) ( 517 )
Based on the first-principles calculations, we firstly predict that RuB2 undergoes a phase transition from the orthorhombic phase to the hexagonal phase with a volume collapse of 1% when the applied pressure is 15.7GPa. The values of calculated elastic moduli indicate that RuB2 and RuN2 are low compressibility materials. Based on the calculated electronic density of states and valence charge density distribution, the bonding nature of RuB2 is examined to obtain a deeper insight into the physical origin of the mechanical properties. The metallicity and high elastic moduli of RuB2 and RuN2 suggest that they are potential hard conductors.
Inherent Shear-Dilatation Coexistence in Metallic Glass
JIANG Min-Qiang, JIANG Si-Yue$, DAI Lan-Hong,
Chin. Phys. Lett. 2009, 26 (1): 016103 .   DOI: 10.1088/0256-307X/26/1/016103
Abstract   PDF(pc) (530KB) ( 440 )
Shear deformation can induce normal stress or hydrostatic stress in metallic glasses [Nature Mater. 2 (2003) 449, Intermetallics 14 (2006) 1033]. We perform the bulk deformation of three-dimensional Cu46Zr54 metallic glass (MG) and Cu single crystal model systems using molecular dynamics simulation. The results indicate that hydrostatic stress can incur shear stress in MG, but not in crystal. The resultant pronounced asymmetry between tension and compression originates from this inherent shear-dilatation coexistence in MG.
This paper has been withdrawn by the first author due to misconduct, see Chin. Phys. Lett. 26, 079901, 2009
In Situ Tests of Multiwalled Carbon Nanotubes with Strength Close to Theoretical Predictions
PENG Bei, Horacio D. Espinosa
Chin. Phys. Lett. 2009, 26 (1): 016104 .   DOI: 10.1088/0256-307X/26/1/016104
Abstract   PDF(pc) (413KB) ( 521 )
Using MEMS technology and transmission electron microscopy we show experimentally multiwalled carbon nanotubes with a mean fracture strength of larger than 100GPa, which exceeds the earlier observations by a factor of approximately 3. These results are in excellent agreement with quantum-mechanical estimations. This performance is made possible by omitting chemical treatments from the sample preparation process, thus avoiding the formation of defects. High-resolution imaging is used to directly determine the number of fractured shells and the chirality of the outer shell. Electron irradiation at 200keV for 10, 100 and 1800s lead to improvements of the maximum sustainable loads by factors of 2.4, 7.9 and 11.6 compared with non-irradiated samples of similar diameter. This effect is attributed to crosslinking between the shells. This procedure is a cost effective way of customizing the properties of multiwall nanotubes for many applications of interest ranging from nanocomposites to nanodevices.
First-Principles Study on Magnetic Properties of V-Doped ZnO Nanotubes
ZHANG Fu-Chun, , ZHANG Zhi-Yong, ZHANG Wei-Hu, , YAN Jun-Feng, YUN Jiang-Ni
Chin. Phys. Lett. 2009, 26 (1): 016105 .   DOI: 10.1088/0256-307X/26/1/016105
Abstract   PDF(pc) (487KB) ( 802 )

Electronic and magnetic properties of V-doped ZnO nanotubes in which one of Zn2+ ions is substituted by V2+ ions are studied by the first-principles calculations of plane wave ultra-soft pseudo-potential technology based on the spin-density function theory. The computational results reveal that spontaneous magnetization in V-doped (9,0) ZnO nanotubes can be induced without p-type or n-type doping treatment, and the ferromagnetism is isotropic and independent of the chirality and diameter of the nanotubes. It is found that V-doped ZnO nanotubes have large magnetic moments and are ferromagnetic half-metal materials. Moreover, the ferromagnetic coupling among V atoms is generated by O 2p electron spins and V 3d electron spins localized at the exchanging interactions between magnetic transitional metal (TM) impurities. The appearance of ferromagnetism in V-doped ZnO nanotubes gives some reference to fabrication of a transparent ferromagnet which may have a great impact on industrial applications in magneto-optical devices.

Interfacial Reactions and Cubic Neodymium Oxide Formation in Low Dispersed Nd2O3-SiO2 System by Wet Chemical Method
S. Duhan, P. Aghamkar,
Chin. Phys. Lett. 2009, 26 (1): 016106 .   DOI: 10.1088/0256-307X/26/1/016106
Abstract   PDF(pc) (401KB) ( 708 )
Neodymium (binary oxide) powders are synthesized by a solgel technique. Prepared powders are heat treated under different temperature for different time duration and obtained nanostructure of Nd. Metal particle have diameters in the range 7.8-21.6nm. It is found that the heat treatment plays an important role to produce different structure of Nd-doped silica matrix. The peak position shifts to lower angle as the size of the nano metal oxide particles size increases.
First-Principles Calculations of Elastic Properties of Cubic Ni2MnGa
CHEN Dong, XIAO Qi-Min, ZHAO Ying-Lu, YU Ben-Hai, WANG Chun-Lei, SHI De-Heng
Chin. Phys. Lett. 2009, 26 (1): 016201 .   DOI: 10.1088/0256-307X/26/1/016201
Abstract   PDF(pc) (359KB) ( 681 )
Dependence of bulk modulus on both pressure and temperature, the elastic constants Cij and the pressure and temperature dependence of normalized volume V/V0 of cubic Ni2MnGa alloy are successfully obtained using the first-principles plane-wave pseudopotential (PW-PP) method as well as the quasi-harmonic Debye model. We analyse the relationship between bulk modulus and temperature up to 800K and obtain the relationships between bulk modulus B and pressures at different temperatures. It is found that the bulk modulus B increases monotonically with increasing pressure. Moreover, the temperature dependences of the Debye temperature are also analysed. The calculated results are in agreement with the available experimental data and the previous theoretical results.
Diamond Structure BeO, Designable Super-Hard Materials and Semiconductor Be-Diamond
XU Ji-An, BI Yan, SUN Zong-Qi, XIE Hong-Sen
Chin. Phys. Lett. 2009, 26 (1): 016202 .   DOI: 10.1088/0256-307X/26/1/016202
Abstract   PDF(pc) (446KB) ( 720 )
It is possible for Beryllium oxide (BeO) to have a cubic diamond structure although it normally has a hexagonal structure under ambient conditions. As the solution of cubic BN and diamond, the solid solution of cubic BeO-diamond or BeO-cBN-diamond can potentially be a kind of super-hard materials with designable hardness; and this solution has also been confirmed based on our preliminary first principles calculations. In addition, the nonstoichiometry of BeO could create a mobile carrier in the cubic BeO-C or BeO-BN-C system and it might lead to a new type of semiconductor Be-diamond.
Shock-Assisted Superficial Hexagonal-to-Cubic Phase Transition in GaN/Sapphire Interface Induced by Using Ultra-violet Laser Lift-Off Techniques
CHEN Wei-Hua, HU Xiao-Dong, SHAN Xu-Dong, KANG Xiang-Ning, ZHOU Xu-Rong, ZHANG Xiao-Min, YU Tong-Jun, YANG Zhi-Jian, YOU Li-Ping, XUKe, ZHANG Guo-Yi
Chin. Phys. Lett. 2009, 26 (1): 016203 .   DOI: 10.1088/0256-307X/26/1/016203
Abstract   PDF(pc) (530KB) ( 548 )

Ultra-violet (KrF excimer laser,λ=248nm) laser lift-off (LLO) techniques have been operated to the GaN/sapphire structure to separate GaN from the sapphire substrate. Hexagonal to cubic phase transformation induced by the ultra-violet laser lift-off (UV-LLO) has been characterized by micro-Raman spectroscopy, micro-photoluminescence, along with high-resolution transmission electron microscopy (HRTEM). HRTEM indicates that UV-LLO induced phase transition takes place above the LLO interface, without phase transition under the LLO interface. The formed cubic GaN often exists as nanocrystal grains attaching on the bulk hexagonal GaN. The half-loop-cluster-like UV-LLO interface indicates that the LLO-induced shock waves has generated and played an assistant role in the decomposition of the hexagonal GaN and in the formation of cubic GaN grains at the LLO surface.

Dynamic Simulation of Kosterlitz-Thouless Transition in Two-Dimensional Fully Frustrated XY Model
LEI Xiao-Wei, ZHAO Xiao-Yu
Chin. Phys. Lett. 2009, 26 (1): 016401 .   DOI: 10.1088/0256-307X/26/1/016401
Abstract   PDF(pc) (588KB) ( 645 )
Relaxation dynamics of the two-dimensional fully frustrated XY model is investigated with Monte Carlo methods. The simulation focuses on the Kosterlitz-Thouless phase transition. From the dynamic scaling behaviour of the magnetization above the transition temperature TKT, the correlating time of the dynamic system is extracted. The transition temperature TKT and static exponent ν are then determined.
Configurational Entropy, Diffusivity and Potential Energy Landscape in Liquid Argon
DUAN Yong-Ping, MA Cong-Xiao, LI Jia-Yun, LI Cong, WANG Dan, LI Mei-Li, SUN Min-Hua
Chin. Phys. Lett. 2009, 26 (1): 016402 .   DOI: 10.1088/0256-307X/26/1/016402
Abstract   PDF(pc) (360KB) ( 580 )

The configurational entropy, diffusion coefficient, dynamics and thermodynamics fragility indices of liquid argon are calculated using molecular dynamics simulations at two densities. The relationship between dynamics and thermodynamics properties is studied. The diffusion coefficient depends linearly on configurational entropy, which is consistent with the hypothesis of Adam-Gibbs. The consistence of dynamics and thermodynamics fragility indices demonstrates that dynamical behaviour is governed by thermodynamics behaviour in glass transition of liquid argon.

First-Principles Calculations of Phase Transition and Stability of Si2CN4 under High Pressure
DU Hui-Jing, GUO Li-Cong, LI Dong-Chun, YU Dong-Li, HE Ju-Long
Chin. Phys. Lett. 2009, 26 (1): 016403 .   DOI: 10.1088/0256-307X/26/1/016403
Abstract   PDF(pc) (438KB) ( 577 )
A pressure-induced phase transition and stability in Si2CN4 polymorphs under high pressure are studied by first-principles calculations. The result shows that the phase transition pressure of α- and β-Si2CN4 to the cubic spinal phase is 29.9GPa and 27.5GPa predicted by thermodynamic method respectively. Under ambient condition, all of the three Si2CN4 polymorphs are metastable with positive formation enthalpy. Unlike the stability of Si3N4 polymorphs, α-Si2CN4 is more stable than the β phase.
Stability Diagrams of a Bose-Einstein Condensate in Excited Bloch Bands
LIANG Zhao-Xin, HU Ban-Bi,
Chin. Phys. Lett. 2009, 26 (1): 016701 .   DOI: 10.1088/0256-307X/26/1/016701
Abstract   PDF(pc) (316KB) ( 399 )
Landau and dynamical instabilities of a Bose-Einstein condensate (BEC) in the excited bands of a one-dimensional optical lattice are investigated by the Gross-Pitaevskii theory. Our results show that there always exists Landau instability for a BEC in the whole region of excited bands.We also map out the dangerous zones of the dynamical instability. The experimental implications of the stability diagram are discussed.
Giant Static Dielectric Constant of Strained PbTiO3
WANG Yuan-Xu
Chin. Phys. Lett. 2009, 26 (1): 016801 .   DOI: 10.1088/0256-307X/26/1/016801
Abstract   PDF(pc) (253KB) ( 867 )
First-principles density functional perturbation calculations are employed to study the dielectric and piezoelectric properties of strained tetragonal PbTiO3. Lattice distortion, static dielectric constant, Born effective charge, zone-centre phonons, and piezoelectric constant are obtained. For the strained tetragonal PbTiO3, we obtain a giant static dielectric constant (3600) under a strain 0.77%. Moreover, the calculated piezoelectric constant e15 of strained PbTiO3 reaches about 203C/m2 which is about 20 times of that of unstrained system. The giant static dielectric constant is mainly due to the softening of the lowest-frequency phonon mode and the reduce of Ti-O bond length. This work demonstrates a route to a giant static dielectrics for electrically microwave and other devices.
Structural Stabilities of Ordered Arrays of Nb4 Clusters on NaCl(100) Surface
WANG Xiao-Chun, ZHANG Jian-Hua, WEN Yu-Hua, ZHU Zi-Zhong
Chin. Phys. Lett. 2009, 26 (1): 016802 .   DOI: 10.1088/0256-307X/26/1/016802
Abstract   PDF(pc) (1189KB) ( 385 )
Adsorption of ordered (2×2) arrays of Nb4 clusters on the insulating surface of NaCl(100) is studied by the first-principles calculations within the density functional theory. The calculations on the relaxed geometries and cohesive energies show that both the tetrahedron and quadrangle-Nb4 can be stably adsorbed on this substrate, which may have important applications. The adsorption of quadrangle-Nb4 on the NaCl(100) surface is more stable than that of tetrahedron-Nb4. Both the Nb4 clusters studied and a single Nb atom prefer the top site of the Cl atom in the NaCl(100) surface. Electronic structure analysis suggests that the interactions between the Nb4 clusters and the substrate are weak
Two-Step Oxidation of Pb(111) Surfaces
JIANG Peng, WANG Li-Li, NING Yan-Xiao, QI Yun, MA Xu-Cun, JIA Jin-Feng, XUE Qi-Kun,
Chin. Phys. Lett. 2009, 26 (1): 016803 .   DOI: 10.1088/0256-307X/26/1/016803
Abstract   PDF(pc) (429KB) ( 544 )
We report on a two-step method for oxidation of Pb(111) surfaces, which consists of low temperature (90K) adsorption of O2 and subsequent annealing to room temperature. In situ scanning tunnelling microscopy observation reveals that oxidation of Pb(111) can occur effectively by this method, while direct room temperature adsorption results in no oxidation. Temperature-dependent adsorption behaviour suggests the existence of a precursor state for O2 adsorption on Pb(111) surfaces and can explain the oxidation-resistance of clean Pb(111) surface at room temperature.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Structural and Thermodynamic Properties of Cerium via First-Principles Plane Wave Method with a Relativistic Analytic Pseudopotential
SUN Li-Li, JI Guang-Fu, CHEN Xiang-Rong, GOU Qing-Quan
Chin. Phys. Lett. 2009, 26 (1): 017101 .   DOI: 10.1088/0256-307X/26/1/017101
Abstract   PDF(pc) (383KB) ( 550 )
We investigate the structural and thermodynamic properties of cerium in α phase by using the first-principles plane wave method with a relativistic analytic pseudopotential of Hartwigsen, Goedcker and Hutter (HGH) scheme in the frame of local density approximation (LDA). The obtained lattice constant and bulk modulus are consistent with the available experimental data. Moreover, dependences of the normalized primitive volume V/V0 on pressure and the thermodynamic quantities (including the Grüneisen constant γ and thermal expansion α) on temperature and pressure are obtained. The obtained linear thermal expansion parameter α (9.857× 10-6K-1 at 293.15K and 0GPa) is slightly larger than the experimental value (6.3×10-6K-1). All the results indicate that we provide an effective method to deal with the ground properties of the strongly interacting d- and/or f-electron systems.
Mechanism for Alternating Electric Fields Induced-Effects on Cytosolic Calcium
LUO Ming-Yan, SONG Kun, ZHANG Xu, LEE Imshik
Chin. Phys. Lett. 2009, 26 (1): 017102 .   DOI: 10.1088/0256-307X/26/1/017102
Abstract   PDF(pc) (428KB) ( 552 )
In this work, from the point of calcium ions in the cytosol, we extend a Vm-[Ca2+]cyt model to explain the changes of action potential Vm of the plasma membrane and the calcium concentration in the cytosol [Ca2+]cyt under an alternating electric field in cells. An alternating external electric field may exert an oscillating force to each of the free electrolytes, existing on both sides of the plasma membrane. The mechanism for the alternating electric field induced-effects on Vm and [Ca2+]cyt is elucidated. The simulation results show a correlation between the changes of [Ca2+]cyt and the alternating electric field. When the numerical ratio between the intensity E0(mV/m) and the frequency υ (Hz) of the field was about 1-2, the [Ca2+]cyt signal is changed dramatically. The bioactive changes of [Ca2+]_cyt appear at low frequency, in the range of 0-100Hz.
Activation of Hydrogen-Passivated Mg in GaN-Based Light Emitting Diode Annealing with Minority-Carrier Injection
YANG Ling, HAO Yue, LI Pei-Xian, ZHOU Xiao-Wei
Chin. Phys. Lett. 2009, 26 (1): 017103 .   DOI: 10.1088/0256-307X/26/1/017103
Abstract   PDF(pc) (452KB) ( 1490 )
We discuss an issue on the activation of p-GaN material under different annealing conditions and study the mechanism for the p-GaN activation. Under annealing in nitrogen, it is found that hydrogen cannot be completely removed from p-GaN. The experiments also indicate that rudimental hydrogen can exist stably in a certain state where hydrogen does not passivate the Mg acceptor in the sample annealing under bias. However, making additional annealing in nitrogen, we find that the steady state hydrogen can be decomposed and the Mg-H complex could generate again. Hydrogen remaining in the layer seems to play a major role in this reversible phenomenon.
Electronic Structure of Eu6C60
WANG Xiao-Xiong, LI Hong-Nian, XU Ya-Bo, WANG, ZHANG Wen-Hua, XU Fa-Qiang
Chin. Phys. Lett. 2009, 26 (1): 017104 .   DOI: 10.1088/0256-307X/26/1/017104
Abstract   PDF(pc) (304KB) ( 424 )
We study the valence band of Eu-intercalated C60 by synchrotron radiation photoelectron spectroscopy to understand the ferromagnetism (FM) and the giant magnetoresistance (GMR) of Eu6C60. The results reveal the semiconducting property and the remarkable 5d6s-π hybridization. Eu-C60 bonding has both ionic and covalent contributions. No more than half the 5d6s electrons transfer from Eu to the LUMO derived band of C60, and the LUMO+1 derived band is not filled. The remaining valence electrons of Eu, together with some π (LUMO, HOMO and HOMO-1) electrons, constitute the covalent bond. The electronic structure implies that the magnetic coupling in Eu6C60 should be through the intra-atomic f-sd exchange and the medium of the π electrons. The possibility of the GMR being tunnelling agnetoresistance is ruled out
Geometric and Electronic Properties of SrCoO2.5: An LSDA+U Study
WU Hai-Ping, DENG Kai-Ming, HU Feng-Lan, TAN Wei-Shi, TANG Chun-Mei, LI Qun-Xiang
Chin. Phys. Lett. 2009, 26 (1): 017105 .   DOI: 10.1088/0256-307X/26/1/017105
Abstract   PDF(pc) (537KB) ( 677 )
The geometric and electronic properties of SrCoO2.5 have been studied using the local-spin density approximation together with the Hubbard method. The geometric optimization shows that the energy of a unit supercell for SrCoO2.5 with the space group Pnma is at least 1.37eV lower than the others, so we infer that the Pnma structure is the ground state of SrCoO2.5 at low temperature. The electronic band structure calculations demonstrate that the paramagnetic ordering SrCoO2.5 at high temperature has the character of an indirect band gap semi-conductor, while the antiferromagnetic ordering SrCoO2.5 at low temperature has the character of a conductor. The magnetism calculation shows that the magnetic moment of Co is 2.96μB, comparable with the experimental measurement at the liquid nitrogen temperature, i.e. 3.30±0.5μB.
Temperature and Thickness Effects on Electrical Properties of InP Films Deposited by Spray Pyrolysis
Refik Kayali, Mehmet Ari, Mustafa Ö, ztacs, Metin Bedir, Funda Aksoy
Chin. Phys. Lett. 2009, 26 (1): 017106 .   DOI: 10.1088/0256-307X/26/1/017106
Abstract   PDF(pc) (242KB) ( 609 )
InP film samples are prepared by spray pyrolysis technique using aqueous solutions of InCl3 and Na2HPO4, which are atomized with compressed air as carrier gas onto glass substrates at 500°C with different thicknesses of the films. The structural properties of the samples are determined by x-ray diffraction (XRD). It is found that the crystal structure of the InP films is polycrystalline hexagonal. The orientations of all the obtained films are along the c-axis perpendicular to the substrate. The electrical measurements of the samples are obtained by dc four-probe technique on rectangular-shape samples. The effects of temperature on the electrical properties of the InP films are studied in detail.
Electronic Structure and Optical Properties of La-Doped SrTiO3 and Sr2TiO4 by Density Function Theory
YUN Jiang-Ni, ZHANG Zhi-Yong, YAN Jun-Feng, ZHAO Wu
Chin. Phys. Lett. 2009, 26 (1): 017107 .   DOI: 10.1088/0256-307X/26/1/017107
Abstract   PDF(pc) (441KB) ( 1777 )

The effect of La doping on the electronic structure and optical properties of SrTiO3 and Sr2TiO4 is investigated by the first-principles calculation of plane wave ultrasoft pseudopotential based on the density function theory (DFT). The calculated results reveal that the electron doping in the case of Sr0.875La0.125TiO3 and Sr1.875La0.125TiO4 can be described within the rigid band model. The La3+ ions fully acts as electron donors in Sr0.875La0.125TiO3 and Sr1.875La0.125TiO4 systems and the Fermi level shifts further into the conduction bands (CBs) for Sr1.875La0.125TiO4 compared to Sr0.875La0.125TiO3. The two systems exhibit n-type degenerate semiconductor features. At the same time, the density of states (DOS) of the two systems shift towards low energies and the optical band gaps are broadened. The Sr1.875La0.125TiO4 is highly transparent with the transmittance about 90% in the visible range, which is larger than that of Sr0.875La0.125TiO3(85%). The wide band gap, small transition probability and weak absorption due to the low partial density of states (PDOS) of impurity in the Fermi level result in the optical transparency of the films...

Negative Magnetoresistivity of ErBi and Its Crystal-Field Levels
LIU Zhao-Sen, Divis Martin, Sechovsky Vladimir
Chin. Phys. Lett. 2009, 26 (1): 017201 .   DOI: 10.1088/0256-307X/26/1/017201
Abstract   PDF(pc) (340KB) ( 501 )
A theoretical approach is generalized and employed in this work to evaluate the magnetoresistivity of ErBi in external magnetic fields. The calculated results and theoretical analyses show that when an external magnetic field is applied in the z-direction, the magnetoresistivity can be reduced considerably due to the degeneracy lifting of the crystal-field levels. However, when the magnetic field is exerted along the x-axis, the magnetoresistivity will be increased because of the formations of new magnetic states of the Er ion and its transitions within and between these new states.
Role of TiO2 Nanotube on Improvement of Performance of Hybrid Photovoltaic Devices
SHI Quan-Min, HOU Yan-Bing, LI Yan, FENG Zhi-Hui, LIU Xiao-Jun
Chin. Phys. Lett. 2009, 26 (1): 017202 .   DOI: 10.1088/0256-307X/26/1/017202
Abstract   PDF(pc) (393KB) ( 480 )
The performance of TiO2 nanotubes in bulk heterojunction of poly (2-methoxy-5-(2'-ethylhexyloxy)-1, 4-phenylenevinylene) (MEH-PPV)/TiO2 nanotubes is investigated. The transport properties are studied by using the time-of-flight technique (TOF). The carrier mobilities of both holes and electrons are not improved for the MEH-PPV:TiO2 composites compared with the pristine MEH-PPV. However, photoluminescence under the influence of the electric field indicates that the dissociation of excitons in the MEH-PPV:TiO2 composites, which is facilitated by photoinduced charge transfer, only requires a smaller electric field.
First-Principles Study of Tetragonal BaTiO3 Subjected to Uniaxial Tensile Stress along the c Axis
WANG Chun-Mei, DUAN Yi-Feng, CHEN Chang-Qing
Chin. Phys. Lett. 2009, 26 (1): 017203 .   DOI: 10.1088/0256-307X/26/1/017203
Abstract   PDF(pc) (381KB) ( 987 )
Tetragonal BaTiO3 under uniaxial tensile stress along the c axis is investigated from first principles. The structural parameters and polarization show a little abrupt change near a critical stress σc of 4.57GPa, which is related to the uniaxial tensile stress induced change of elastic constants. We also find that the ferroelectric lattice distortion increases with the increasing stress. Moreover, it is found that uniaxial tensile stress can enhance the piezoelectric strain coefficients, which reach their maximum values at the stress σc.
Properties of AlyGa1-yN/AlxGa1-xN/AlN/GaN Double-Barrier High Electron Mobility Transistor Structure
GUO Lun-Chun, WANG Xiao-Liang, XIAO Hong-Ling, RAN Jun-Xue, Wang Cui-Mei, MA Zhi-Yong, LUO Wei-Jun, WANG Zhan-Guo
Chin. Phys. Lett. 2009, 26 (1): 017301 .   DOI: 10.1088/0256-307X/26/1/017301
Abstract   PDF(pc) (438KB) ( 527 )
Electrical properties of AlyGa1-yN/AlxGa1-xN/AlN/GaN structure are investigated by solving coupled Schrödinger and Poisson equation self-consistently. Our calculations show that the two-dimensional electron gas (2DEG) density will decrease with the thickness of the second barrier (AlyGa1-yN) once the AlN content of the second barrier is smaller than a critical value yc, and will increase with the thickness of the second barrier (AlyGa1-yN) when the critical AlN content of the second barrier yc is exceeded. Our calculations also show that the critical AlN content of the second barrier yc will increase with the AlN content and the thickness of the first barrier layer (AlxGa1-xN).
Modified Josephson Equation for Mesoscopic Parallel LC Circuit Including a Josephson Junction
SU Jie, WANG Ji-Suo, LIANG Bao-Long, ZHANG Xiao-Yan
Chin. Phys. Lett. 2009, 26 (1): 017302 .   DOI: 10.1088/0256-307X/26/1/017302
Abstract   PDF(pc) (272KB) ( 683 )

By introducing the entangled state representation, the Cooper-pair number-phase quantization of the mesoscopic parallel LC circuit including a Josephson junction is realized. In the Heisenberg picture, the modified Josephson equation associated with the modification of the Faraday equation about the inductance is deduced from the motion equation.

Optimizing Design of Breakdown Voltage to Eliminate Back Gate Bias Effect in Silicon-on-Insulator Diode Using Low Doping Buried Layer
HO Chi-Hon, LIAO Chien-Nan, CHIEN Feng-Tso, TSAI Yao-Tsung
Chin. Phys. Lett. 2009, 26 (1): 017303 .   DOI: 10.1088/0256-307X/26/1/017303
Abstract   PDF(pc) (540KB) ( 631 )
This work presents the optimal design of a silicon-on-insulator (SOI) diode structure to eliminate the back gate bias effect and to improve breakdown voltage. The SOI structure is characterized by inserting a silicon low doping buried layer (LDBL) between the silicon layer and the buried oxide layer. The LDBL thickness is a key parameter that affects the strong inversion condition of the back MOS capacitor of the new SOI diode. The optimal LDBL thickness in the SOI diode is 2.65μm. The LDBL shielding layer improved the breakdown voltage.
Hot-Carrier Stress Effects on GIDL and SILC in 90nm LDD-MOSFET with Ultra-Thin Gate Oxide
HU Shi-Gang, HAO Yue, MA Xiao-Hua, CAO Yan-Rong, CHEN Chi, WU Xiao-Feng
Chin. Phys. Lett. 2009, 26 (1): 017304 .   DOI: 10.1088/0256-307X/26/1/017304
Abstract   PDF(pc) (589KB) ( 1725 )
Hot-carrier degradation for 90nm gate length lightly-doped drain (LDD) NMOSFET with ultra-thin (1.4nm) gate oxide is investigated under the low gate voltage stress (LGVS) and peak substrate current (Isub,max) stress. It is found that the degradation of device parameters exhibits saturating time dependence under the two stresses. We concentrate on the effect of these two stresses on gate-induced-drain leakage (GIDL) current and stress induced leakage current (SILC). The characteristics of the GIDL current are used to analyse the damage generated in the gate-to-LDD region during the two stresses. However, the damage generated during the LGVS shows different characteristics from that during Isub,max stress. SILC is also investigated under the two stresses. It is found experimentally that there is a linear correlation between the degradation of SILC and that of threshold voltage during the two stresses. It is concluded that the mechanism of SILC is due to the combined effect of oxide charge trapping and interface traps for the ultra-short gate length and ultra-thin gate oxide LDD NMOSFETs under the two stresses.
Fantastic Behaviour of High-TC Superconductor Junctions: Tunable Superconductivity
CHEN Yuan-Sha, ZHANG Yan, LIAN Gui-Jun, XIONG Guang-Cheng
Chin. Phys. Lett. 2009, 26 (1): 017305 .   DOI: 10.1088/0256-307X/26/1/017305
Abstract   PDF(pc) (415KB) ( 422 )
Carrier injection performed in oxygen-deficient YBa2Cu3O7-δ (YBCO) hetero-structure junctions exhibits tunable resistance that is entirely different from the behaviour of semiconductor devices. Tunable superconductivity in YBCO junctions, increasing over 20K in transition temperature, has achieved by using electric processes. To our knowledge, this is the first observation that intrinsic property of high TC superconductors' superconductivity can be adjusted as tunable functional parameters of devices. The fantastic phenomenon caused by carrier injection is discussed based on a proposed charge carrier self-trapping model and BCS theory.
Enhanced Orbital Degeneracy in Momentum Space for LaOFeAs
ZHANG Hai-Jun, XU Gang, DAI Xi, FANG Zhong
Chin. Phys. Lett. 2009, 26 (1): 017401 .   DOI: 10.1088/0256-307X/26/1/017401
Abstract   PDF(pc) (573KB) ( 591 )
The Fermi surfaces (FS) of LaOFeAs (in kz=0 plane) consist of two hole-type circles around Γ point, which do not touch each other, and two electron-type co-centred ellipses around the M point, which are degenerate along the M-X line. By first-principles calculations, here we show that additional degeneracy exists for the two electron-type FS, and the crucial role of F-doping and pressure is to enhance this orbital degeneracy. It is therefore suggested that the inter-orbital fluctuation is important to understand the unconventional superconductivity in these materials.
Superconductivity and Transport Properties in Th and F Codoped Sm1-xThxFeAsO1-yFy
LI Yu-ke, LIN Xiao, TAO Qian, CHEN Hang, WANG Cao, LI Lin-Jun, LUO Yong-Kang, HE Mi, ZHU Zeng-Wei, CAO Gang-Han, XU Zhu-An
Chin. Phys. Lett. 2009, 26 (1): 017402 .   DOI: 10.1088/0256-307X/26/1/017402
Abstract   PDF(pc) (531KB) ( 485 )
A series of Th and F co-doped superconductors Sm1-xThxFeAsO1-yFy are synthesized and the variation of superconductivity with the doping level is investigated. At the fixed Th doping level x = 0.1, the superconducting transition temperature Tc increases monotonically with F content, and finally Tc reaches a maximum of about 55K around y = 0.1, and saturates for even more F content (y = 0.15). Similar to the SmFeAsO1-yFy system, the normal state thermopower increases monotonically with the doping level. However the decrease of Tc in the `overdoped' regime is not observed and possible explanation is discussed.
Microwave Magnetic Permeability of Fe3O4 Nanoparticles
ZHENG Hong, YANG Yong, WEN Fu-Sheng, YI Hai-Bo, ZHOU Dong, LI Fa-Shen
Chin. Phys. Lett. 2009, 26 (1): 017501 .   DOI: 10.1088/0256-307X/26/1/017501
Abstract   PDF(pc) (389KB) ( 947 )
Well-dispersed Fe3O4 nanoparticles are synthesized via an oxidization method with NaNO2 as oxidant. The microwave magnetic properties of the composites are studied with different volume fractions of Fe3O4 nanoparticles. It is found that a lower volume fraction corresponds to a higher magnetic resonance frequency. This could be ascribed to the enhancement of exchange interaction with a weakened dipolar interaction when the volume fraction decreases.
Vortex Pinning due to Dynamic Spin-Vortex Interaction in aSuperconductor/Ferromagnet Multilayer
WU Hong-Ye, ZOU Tao, CHENG Zhao-Hua, SUN Young
Chin. Phys. Lett. 2009, 26 (1): 017502 .   DOI: 10.1088/0256-307X/26/1/017502
Abstract   PDF(pc) (341KB) ( 482 )
We investigate the mutual interaction between superconductivity and ferromagnetism in a Nb/Ni81Fe19 multilayer by ac susceptibility measurements. Compared with a pure superconducting Nb film, the critical current density of the multilayer is apparently enhanced in a low magnetic field region but remains nearly the same in high magnetic fields, which indicates that a continuous ferromagnetic layer with in-plane magnetization can produce strong vortex pinning in a low field region. We interpret this unusual vortex-pinning phenomenon as a consequence of dynamic spin-vortex interaction which induces a spin rotation following vortex movement. In addition, we propose that this dynamic interaction could be used for spin manipulation via a superconductor.
Influence of Temperature on Equilibrium Separation Between Vertical Bloch Lines in OHBs in Garnet Bubble Films
SUN Hui-Yuan, HU Yun-Zhi, LIU Li-Hu
Chin. Phys. Lett. 2009, 26 (1): 017503 .   DOI: 10.1088/0256-307X/26/1/017503
Abstract   PDF(pc) (313KB) ( 400 )
The diameters of the ordinary hard bubbles (OHBs) and soft bubbles in epitaxial garnet films are measured under the microscope at various temperatures. It is found that the bubble diameters of OHBs increase with temperature, and it is concluded that the equilibrium separation between two neighbouring vertical Bloch lines (VBLs) Seq is widened with increasing temperature. At the same time, the results can be understood simply as that there are more VBLs in the domain walls of the first dumbbell domains (IDs) than those in walls of OHBs at the same temperature.
On Room-Temperature Inversion of EPR Signals of P1 Centre in Synthetic Diamond
G. G. Fedoruk, O. N. Poklonskaya
Chin. Phys. Lett. 2009, 26 (1): 017601 .   DOI: 10.1088/0256-307X/26/1/017601
Abstract   PDF(pc) (254KB) ( 502 )
Room-temperature inversion of EPR absorption signals of P1 centre in synthetic diamond is studied by the transient nutation technique. Use of the bichromatic field, consisting of a transverse microwave field and longitudinal radio frequency field, allows to investigate the dynamics of P1 centres in the same field configuration as in cw EPR spectrometers. It is shown that the annealing decreases the P1 centre concentration and, respectively, increases the spin-spin relaxation time. As a result, the periodic inversion (nutation) of the P1 centre absorption signal is observed longer. It is assumed that the P1 centre signal inversion, which was previously observed by cw EPR, might be caused by the Bloch-Siegert effect in the bichromatic field.
Correlation between Imprint and Long-Time Polarization Reversal under Low Fields in Ferroelectric Thin Films
JIANG An-Quan, TANG Ting-Ao
Chin. Phys. Lett. 2009, 26 (1): 017701 .   DOI: 10.1088/0256-307X/26/1/017701
Abstract   PDF(pc) (339KB) ( 502 )
Time interval of slow polarization reversal in ferroelectric thin films is broadened over more than two decades to disobey the classical Kolmogorov-Avrami--Ishibashi (KAI) equation as the applied field approaches the coercive field of domain switching. The assumption of a Lorentzian distribution of logarithmic waiting times of reversed domain nucleation in this equation can resolve this dilemma. In our work, we explain this equation from the coercive-voltage distribution in thin films, and derive a similar function to describe slow polarization reversal from the consideration of a long-time imprint effect rather than the KAI model.
Stimulated Emission from a TiO2 Particle-Dispersed Dye Polymer Plane Waveguide
WANG Qiong, YE Li-Hua, XI Jun, LU Chang-Gui, HU Guo-Hua, FANG Min, CUI Yi-Ping
Chin. Phys. Lett. 2009, 26 (1): 017801 .   DOI: 10.1088/0256-307X/26/1/017801
Abstract   PDF(pc) (424KB) ( 466 )
We report the stimulated emission from a dye doped polymer plane waveguide with TiO2 particles. This waveguide consists of a poly (methylmethacrylate) (PMMA) film containing laser dye DCM as a gain medium. The emission spectrum of the film pumped by the Nd:YAG laser is different from the amplified spontaneous emission of the dye-doped film without particles. It is shown that when the excitation intensity reaches the threshold
9.6μJ, the broad band emission spectrum narrows into multiple separate peaks with central wavelength of 608nm. The linewidth of the sharp peak is 0.5nm. According to our analyses, this phenomenon is due to the multiscattering of the disordered TiO2 particles inside the gain polymer film.
Temperature Insensitivity of Optical Properties of InAs/GaAs Quantum Dots due to a Pregrown InGaAs Quantum Well
LIANG Zhi-Mei, JIN Can, JIN Peng, WU Ju, WANG Zhan-Guo
Chin. Phys. Lett. 2009, 26 (1): 017802 .   DOI: 10.1088/0256-307X/26/1/017802
Abstract   PDF(pc) (343KB) ( 504 )
Both the peak position and linewidth in the photoluminescence spectrum of the InAs/GaAs quantum dots usually vary in an anomalous way with increasing temperature. Such anomalous optical behaviour is eliminated by inserting an In0.2Ga0.8As quantum well below the quantum dot layer in molecular beam epitaxy. The insensitivity of the photoluminescence spectra to temperature is explained in terms of the effective carrier redistribution between quantum dots through the In0.2Ga0.8As quantum well.
Amplified Spontaneous Emission of Organic Pyridinium Dye doped Polymeric Waveguide
XI Jun, YE Li-Hua, WANG Qiong, XU Deng, LU Chang-Gui, HU Guo-Hua, CUI Yi-Ping
Chin. Phys. Lett. 2009, 26 (1): 017803 .   DOI: 10.1088/0256-307X/26/1/017803
Abstract   PDF(pc) (445KB) ( 541 )
An organic dye salt trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium iodide (ASPI) is doped with an electron transport organic molecule tris(8-hydroxyquinoline) aluminium (Alq3) in a host matrix of poly(methylmethacrylate) (PMMA), and the amplified spontaneous emission (ASE) is studied. By efficient Forster energy transfer from Alq3 to ASPI, it is demonstrated that the ASE threshold of ASPI:Alq3:PMMA waveguide (about 11μJ/pulse) is much lower than that of ASPI:PMMA system (about 38μJ/pulse). Meanwhile, the peak position of ASE can be controlled by the effect of film thickness on waveguide modes. We show that the ASE peak position can be tuned over 37nm. These characteristics indicate the ASPI:Alq3 system as a promising gain medium for optical amplifiers and organic semiconductor lasers.
Magneto-optical Kerr Effect in Co/Alq3 Granular Films
YIN Jian-Fang, NI Gang, WU Jun-Qi, YUAN Ming-Yun, SHENG Peng, WANG Song-You, JIN Qing-Yuan,
Chin. Phys. Lett. 2009, 26 (1): 017804 .   DOI: 10.1088/0256-307X/26/1/017804
Abstract   PDF(pc) (527KB) ( 614 )
A series of Co/Alq3 granular film samples are prepared using co-evaporating technique. The microstructures and magnetic properties are investigated. The Kerr spectra and optical constants of Cox(Alq3)1-x (0.19≤x≤1) granular films are measured using a magneto-optical Kerr spectrometer and a spectroscopic ellipsometer in the 1.5-4.5eV photon energy range. The Kerr rotation reaches
the maximum value of 0.5° in the x=0.65 sample. The relationship between enhanced Kerr rotation and optical constants is discussed, and the concentration dependence of MOKE spectra is also investigated.
Laser-Induced Damage Growth on Larger-Aperture Fused Silica Optical Components at 351nm
HUANG Wan-Qing, HAN Wei, WANG Fang, XIANG Yong, LI Fu-Quan, FENG Bin, JING Feng, WEI Xiao-Feng, ZHENG Wan-Guo, ZHANG Xiao-Min
Chin. Phys. Lett. 2009, 26 (1): 017901 .   DOI: 10.1088/0256-307X/26/1/017901
Abstract   PDF(pc) (596KB) ( 605 )
Laser-induced damage is a key lifetime limiter for optics in high-power laser facility. Damage initiation and growth under 351nm high-fluence laser irradiation are observed on larger-aperture fused silica optics. The input surface of one fused silica component is damaged most severely and an explanation is presented. Obscurations and the area of a scratch on it are found to grow exponentially with the shot number. The area of damage site
grows linearly. Micrographs of damage sites support the micro-explosion damage model which could be used to qualitatively explain the phenomena.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Molecular Beam Epitaxy of GaSb on GaAs Substrates with AlSb Buffer Layers
ZHOU Zhi-Qiang, XU Ying-Qiang, HAO Rui-Ting, TANG Bao, REN Zheng-Wei, NIU Zhi-Chuan
Chin. Phys. Lett. 2009, 26 (1): 018101 .   DOI: 10.1088/0256-307X/26/1/018101
Abstract   PDF(pc) (482KB) ( 1041 )

We investigate the molecular beam epitaxy growth of GaSb films on GaAs substrates using AlSb buffer layers. Optimization of AlSb growth parameter is aimed at obtaining high GaSb crystal quality and smooth GaSb surface. The optimized growth temperature and thickness of AlSb layers are found to be 450°C and 2.1nm, respectively. A rms surface roughness of 0.67nm over 10×10μm2 is achieved as a 0.5μm GaSb film is grown under optimized conditions.

Low-Temperature (<100°C) Poly-Si Thin Film Fabrication on Glass
WANG Cheng-Long, FAN Duo-Wang, SUN Shuo, ZHANG Fu-Jia, LIU Hong-Zhong
Chin. Phys. Lett. 2009, 26 (1): 018102 .   DOI: 10.1088/0256-307X/26/1/018102
Abstract   PDF(pc) (352KB) ( 790 )

Polycrystalline silicon (poly-Si) thin-film is fabricated on Al-coated planar glass substrates at the temperature below 100°C, using aluminium-induced crystallized (AIC) amorphous silicon (a-Si) deposited by dc-magnetron sputtering under an electric field. The properties of NA poly-Si films (AIC of dc-magnetron sputtered silicon non-annealing) are characterized by Raman spectroscopy and x-ray diffraction (XRD) spectroscopy. A narrow and symmetrical Raman peak at a wave number of about 521cm-1 is observed for samples, showing that the films are fully crystallized. XRD spectra reveal that the films are preferentially (111) oriented. Furthermore, the XRD spectrum of the sample prepared without electric field does not show any XRD peaks for poly-Si, which only appears at about 38°for Al (111) orientation. It is indicated that the electric field plays an important role in crystallization of poly-Si during the dc-magnetron sputtering. Thus, high quality poly-Si film can be obtained at low temperature and separate post-deposition step of AIC of a-silicon can be avoided.

Performances of ZnO-Based Dye Sensitized Solar Cells Fabricated by Hydrothermal Synthesis and Sol-Gel Technique
ZHU Li, FAN Yu-Qing, ZHAO Mao-Cong, WU Min, ZHANG Jia-Yu, XU Chun-Xiang, CUI Yi-Ping
Chin. Phys. Lett. 2009, 26 (1): 018401 .   DOI: 10.1088/0256-307X/26/1/018401
Abstract   PDF(pc) (430KB) ( 1222 )
ZnO is introduced as an alternative to TiO2 in dye sensitized solar cells (DSSCs) due to its band gap similar to TiO2, higher electron mobility, and flexible procedures of preparations. Several samples of ZnO films are prepared with the hydrothermal synthesis method and the sol-gel technique, respectively. These ZnO films were assembled as photoanodes in DSSCs using N3 dye as the sensitizer. The ZnO-based cells prepared by the hydrothermal synthesis show typical current source characteristics, whose fill factor (FF) is 0.44 and photo-to-electric power conversion efficiency is 0.34%. On the other hand, all the samples prepared with the sol-gel technique show accompanied source characteristics with relatively higher power conversion efficiencies (1%) but a lower FF (0.26). X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements indicate that the sol-gel samples have small particles sizes. Therefore, sol-gel samples could adsorb more dye molecules to generate high conversion efficiencies. At the same time, more grain boundaries make it more possible for injected electrons to recombine with the oxidized electrolyte. Hydrothermal samples have bigger grains, so they show poor conversion efficiency and relatively high FF.
A Closed-Form Model for Position-Dependent Potential across the Channel in DG-MOSFETs
LI Meng, TANG Jian-Shi, LV Yang, YU Zhi-Ping
Chin. Phys. Lett. 2009, 26 (1): 018501 .   DOI: 10.1088/0256-307X/26/1/018501
Abstract   PDF(pc) (304KB) ( 470 )
A closed-form model for electrostatic potential distribution in the direction normal to the channel for double-gate (DG) MOSFETs is presented. The effects of doping (NA for nMOS) and minority carriers both are taken into account for the first time, in solving Poisson's equation analytically. Excellent agreement between model-predicted results and numerical device simulation is achieved for a wide range of body thickness, light or high channel-doping, under various bias conditions. This complete closed form for position-dependent potential distribution has wide applications for MOS compact modelling and device design.
Dual-Material Surrounding-Gate Metal-Oxide-Semiconductor Field Effect Transistors with Asymmetric Halo
LI Zun-Chao
Chin. Phys. Lett. 2009, 26 (1): 018502 .   DOI: 10.1088/0256-307X/26/1/018502
Abstract   PDF(pc) (247KB) ( 652 )
Asymmetrical halo and dual-material gate structure are used in the sub-100nm surrounding-gate metal-oxide-semiconductor field effect transistor (MOSFET) to improve the performance. Using three-region parabolic potential distribution and universal boundary condition, analytical surface potential and threshold voltage models of the novel MOSFET are developed based on the solution of Poisson's equation. The performance of the MOSFET is examined by the analytical models and the 3D numerical device simulator Davinci. It is shown that the novel MOSFET can suppress short channel effect and improve carrier transport efficiency. The derived analytical models agree well with Davinci.
Evolutionary Prisoner's Dilemma Game Based on Pursuing Higher Average Payoff
LI Yu-Jian, WANG Bing-Hong, , YANG Han-Xin, LING Xiang, CHEN Xiao-Jie, JIANG Rui
Chin. Phys. Lett. 2009, 26 (1): 018701 .   DOI: 10.1088/0256-307X/26/1/018701
Abstract   PDF(pc) (376KB) ( 527 )
We investigate the prisoner's dilemma game based on a new rule: players will change their current strategies to opposite strategies with some probability if their neighbours' average payoffs are higher than theirs. Compared with the cases on regular lattices (RL) and Newman-Watts small world network (NW), cooperation can be best enhanced on the scale-free Barabási-Albert network (BA). It is found that cooperators are dispersive on RL network, which is different from previously reported results that cooperators will form large clusters to resist the invasion of defectors. Cooperative behaviours on the BA network are discussed in detail. It is found that large-degree individuals have lower cooperation level and gain higher average payoffs than that of small-degree individuals. In addition, we find that small-degree individuals more frequently change strategies than do large-degree individuals.
Sexually Transmitted Diseases on Bipartite Graph
WEN Luo-Sheng, ZHONG Jiang, YANG Xiao-Fan
Chin. Phys. Lett. 2009, 26 (1): 018702 .   DOI: 10.1088/0256-307X/26/1/018702
Abstract   PDF(pc) (269KB) ( 501 )
We study the susceptible--infected--susceptible (SIS) epidemic model on bipartite graph. According to the difference of sex conception in western and oriental nations, we construct the Barabási Albert--Barabási Albert (BA-BA) model and Barabási-Albert Homogeneity (BA-HO) model for sexually transmitted diseases (STDs). Applying the rate equation approach, the positive equilibria of both models are given analytically. We find that the ratio between infected females and infected males is distinctly different in both models and the infected density in the BA-HO model is much less than that in the BA-BA model. These results explain that the countries with small ratio have less infected density than those with large ratio. Our numerical simulations verify these theoretical results.
Local Magnetic Nanoparticle Delivery in Microvasculature
GUO Ping, LI Xin-Xia, XIONG Ping, HE Ji-Shan
Chin. Phys. Lett. 2009, 26 (1): 018703 .   DOI: 10.1088/0256-307X/26/1/018703
Abstract   PDF(pc) (344KB) ( 607 )
The transport and capture of therapeutic magnetic nanoparticles in human microvasculature is studied numerically. The nanoparticles are injected into a vascular system upstream from malignant tissue, and are captured at the tumour site with the aid of a local applied magnetic field positioned outside the body. Taking into account the dominant magnetic and fluidic forces on the particles, our study shows that the nanoparticles can be directed to and concentrated at the desired zone that is within a few centimetres from the surface of the body. In addition, influence of the particles size, average blood flow velocity and the diameter of the blood vessel on the captured efficiency are parametrically analysed.
Dynamics of Symmetric Conserved Mass Aggregation Model on Complex Networks
HUA Da-Yin
Chin. Phys. Lett. 2009, 26 (1): 018901 .   DOI: 10.1088/0256-307X/26/1/018901
Abstract   PDF(pc) (249KB) ( 398 )
We investigate the dynamical behaviour of the aggregation process in the symmetric conserved mass aggregation model under three different topological structures. The dispersion σ (t,L)=(∑i(mi0)2/L)1/2 is defined to describe the dynamical behaviour where ρ0 is the density of particle and mi is the particle number on a site. It is found numerically that for a regular lattice and a scale-free network, σ(t,L) follows a power-law scaling σ(t,L)tδ1 and σ (t,L)~tδ4 from a random initial condition to the stationary states, respectively. However, for a small-world network, there are two power-law scaling regimes, σ(t,L)~ tδ2 when t<T and σ(t,L)~ tδ3 when t>T. Moreover, it is found numerically that δ2 is near to δ1 for small rewiring probability q, and δ3 hardly changes with varying $q$ and it is almost the same as δ4. We speculate that the aggregation of the connection degree accelerates the mass aggregation in the initial relaxation stage and the existence of the long-distance interactions in the complex networks results in the acceleration of the mass aggregation when t>T for the small-world networks. We also show that the relaxation time τ follows a power-law scaling τ ~ Lz and σ (t,L) in the stationary state follows a power-law σ s(L)~Lα for three different structures.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
Correlations between Strong Range Spread-F and GPS L-Band Scintillations Observed in Hainan in 2004
WANG Guo-Jun, SHI Jian-Kui, SHANG She-Ping, WANG Xiao
Chin. Phys. Lett. 2009, 26 (1): 019401 .   DOI: 10.1088/0256-307X/26/1/019401
Abstract   PDF(pc) (865KB) ( 593 )
Data from the DPS-4 digisonde and the GPS L-band ionospheric scintillation monitor are employed to study the correlations between strong range spread-F (SSF) and GPS L-band scintillations observed in the ionosphere over Hainan Island, China (19.5°N, 109.1°E geogr., dip lat. 9°N) in 2004. The SSF in the ionogram is different from the general range spread-F because it extends in frequency well beyond FoF2 and makes FoF2 difficult to be determined. The observations show that the SSF phenomenon is frequently accompanied by the occurrence of GPS L-band scintillations. The SSF and GPS L-band scintillations occur frequently in the equinoctial months (March, April, September, and October), but rarely in the winter (January, February, November, and December) and summer (May-August); especially, occurrence variations of the SSF and GPS L-band scintillations nearly have a same trend. The SSF and scintillations may be associated with the occurrence of topside plasma bubbles and could be explained by the generalized Rayleigh-Taylor instability.
Electron Acceleration by a Finite-Amplitude Solitary Kinetic Alfvén Wave
WANG De-Yu
Chin. Phys. Lett. 2009, 26 (1): 019601 .   DOI: 10.1088/0256-307X/26/1/019601
Abstract   PDF(pc) (219KB) ( 406 )
The electron acceleration by a finite-amplitude solitary kinetic Alfvén wave (SKAW) in the low-β magnetized plasma is presented. It is found that the electron can be efficiently accelerated in both the parallel and the transverse directions of ambient magnetic field by a finite-amplitude SKAW up to several tenfold Alvén velocity within the time 0.08μs. These results are greatly different from the case of the electron accelerated by a small-amplitude SKAW.
104 articles